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Dapr integrates with pub/sub message buses to provide applications with the ability to create event-driven, loosely coupled architectures where producers send events to consumers via topics.

Dapr supports the configuration of multiple, named, pub/sub components per application. Each pub/sub component has a name and this name is used when publishing a message topic. Read the API reference for details on how to publish and subscribe to topics.

Pub/sub components are extensible. A list of support pub/sub components is here and the implementations can be found in the components-contrib repo.

Component files

A pub/sub is described using a Component file:

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: pubsub
  namespace: default
spec:
  type: pubsub.<NAME>
  version: v1
  metadata:
  - name: <KEY>
    value: <VALUE>
  - name: <KEY>
    value: <VALUE>
...

The type of pub/sub is determined by the type field, and properties such as connection strings and other metadata are put in the .metadata section. Even though metadata values can contain secrets in plain text, it is recommended you use a secret store using a secretKeyRef.

Topic creation

Depending on the pub/sub message bus you are using and how it is configured, topics may be created automatically. Even if the message bus supports automatic topic creation, it is a common governance practice to disable it in production environments. You may still need to use a CLI, admin console, or request form to manually create the topics required by your application.

While all pub/sub components support consumerID metadata, the runtime creates a consumer ID if you do not supply one. All component metadata field values can carry templated metadata values, which are resolved on Dapr sidecar startup. For example, you can choose to use {namespace} as the consumerGroup to enable using the same appId in different namespaces using the same topics as described in this article.

Visit this guide for instructions on configuring and using pub/sub components.

Related links

• Overview of the Dapr Pub/Sub building block
• Try the Pub/Sub quickstart sample
• Read the guide on publishing and subscribing
• 了解topic范围
• Learn about message time-to-live
• Learn how to configure Pub/Sub components with multiple namespaces
• List of pub/sub components
• Read the API reference

HowTo: Configure Pub/Sub components with multiple namespaces

Use Dapr Pub/Sub with multiple namespaces